I just recently had to swap out the 3rd, aka "high mount", brake light
bulb in our 2002 Nissan Altima.

It was a fairly simple procedure but I took pictures of the steps and
created a quick guide.

Here's the page -
http://www.paulstravelpictures.com/Nissan-Altima-Third-Brake-Light-Bulb-Replacement-Guide

I'm sure most of you could do this in your sleep, but hopefully it
will help out some of the new owners.

Cheers,
Paul Michaels
Ft. Lauderdale, FL